[Telemetry] Remove session_restore's use of PageTest.CanRunForPage.

tools/perf/benchmarks/session_restore.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import os
 import tempfile
 
 from measurements import session_restore
 import page_sets
 from profile_creators import small_profile_creator
 from telemetry import benchmark
 from telemetry.page import profile_generator
 
 
 class _SessionRestoreTest(benchmark.Benchmark):
+  """Create a session restore test that is either "warm" or "cold".

[qyearsley, 2015/01/28 19:39:08]

1. Possible alternative phrasing: "Base Benchmark class for session restore
benchmarks."

2. Could be re-named _SesssionRestoreTypical25 since the page set is now set in
the base class.

What is done before measurement in a "warm" test? Is it that the browser is
launched and a session restore is done first, then the tabs are closed without
closing the browser, and the session is restored again?

[slamm, 2015/02/23 23:46:35]

Done.

+
+  Use Typical25PageSet to match what the SmallProfileCreator uses.
+  TODO(slamm): Make SmallProfileCreator and this use the same page_set ref.
+  """
+  page_set = page_sets.Typical25PageSet
 
   @classmethod
   def ProcessCommandLineArgs(cls, parser, args):
     super(_SessionRestoreTest, cls).ProcessCommandLineArgs(parser, args)
     profile_type = 'small_profile'
     if not args.browser_options.profile_dir:
       output_dir = os.path.join(tempfile.gettempdir(), profile_type)
       profile_dir = os.path.join(output_dir, profile_type)
       if not os.path.exists(output_dir):
         os.makedirs(output_dir)
 
       # Generate new profiles if profile_dir does not exist. It only exists if
       # all profiles had been correctly generated in a previous run.
       if not os.path.exists(profile_dir):
         new_args = args.Copy()
         new_args.pageset_repeat = 1
         new_args.output_dir = output_dir
         profile_generator.GenerateProfiles(
             small_profile_creator.SmallProfileCreator, profile_type, new_args)
       args.browser_options.profile_dir = profile_dir
 
+  def CreateUserStorySet(self, _):
+    """Return a user story set that only has the first user story.
+
+    The session restore measurement skips the navigation step and
+    only tests session restore by having the browser start-up.
+    The first user story is used to get WPR set up and hold results.
+    """
+    user_story_set = self.page_set()
+    for user_story in user_story_set.user_stories[1:]:
+      user_story_set.RemoveUserStory(user_story)
+    return user_story_set
+
   def CreatePageTest(self, options):
     is_cold = (self.tag == 'cold')
     return session_restore.SessionRestore(cold=is_cold)
 
 # crbug.com/325479, crbug.com/381990
 @benchmark.Disabled('android', 'linux', 'reference')
 class SessionRestoreColdTypical25(_SessionRestoreTest):
   tag = 'cold'
-  page_set = page_sets.Typical25PageSet
   options = {'pageset_repeat': 5}
 
 
 # crbug.com/325479, crbug.com/381990
 @benchmark.Disabled('android', 'linux', 'reference')
 class SessionRestoreWarmTypical25(_SessionRestoreTest):
   tag = 'warm'
-  page_set = page_sets.Typical25PageSet
   options = {'pageset_repeat': 20}